what is difference between `suspendedTransactionAsync ` and kotlinlang #exposed

i know one of them return Deferred and other the direct value. But i see that both of them suspend at the time of call, i.e. if `suspendedTransactionAsync()`suspends at the time of call then what is use of

await()

on the deferred? Like

CoroutineScope.async()

doesn't suspend at the time of call but rather when

await()

is called on that right, so what's difference b/w them(transactions)?

tapac

12/02/2019, 5:15 PM

https://github.com/JetBrains/Exposed/wiki/Transactions#working-with-coroutines

Animesh Sahu

12/02/2019, 5:19 PM

@tapac its not explained there perfectly, why does suspendedTransactionAsync() suspends, again the library is complex so cannot go one by one to calls... Async things should not suspend since they just launch coroutine, whereas it should suspend when we are waiting for the result in await(), i don't understand its behavior

tapac

12/02/2019, 5:20 PM

It suspend on a dispatcher thread and shouldn't block your main thread execution.

Animesh Sahu

12/02/2019, 5:30 PM

@tapac why does it suspend?

tapac

12/02/2019, 5:31 PM

From documentation:

Because Exposed uses JDBC-api to interact with databases that was designed in an era of blocking apis.

Please note what such code remains blocking (as it still uses JDBC) and you should not try to share a transaction between multiple threads as it will lead to undefined behaviour.

Animesh Sahu

12/02/2019, 5:32 PM

Copy code

val job = async(<http://Dispatchers.IO|Dispatchers.IO>) { // it does not suspend here at this line
    // suspendable tasks
}

hob.await() //it does suspend here and should

tapac

12/02/2019, 5:33 PM

It works just like this when you use

suspendedTransactionAsync

Animesh Sahu

12/02/2019, 5:35 PM

Compiler shows it suspends

Ohh got it, it suspend for scope creation not for async execution, its confusing since no definition of methods.

Anyways thanks for your valueable time 🙂

👌 2

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